In wireless communication, devices send and receive messages without being physically coupled. Wireless devices can include portable computers, telephones, location sensors (such as those using GPS), and the like. Portable computers with wireless communication capability can be coupled to a computer network, such as the Internet or the World Wide Web. The IEEE 802.11 standard (including 802.11a, 802.11b, and 802.11g) is one known technique for coupling wireless devices to a computer network. In 802.11, wireless devices seek out and select “access points” (herein sometimes called “AP's”), which are themselves physically coupled, for computer communication, to at least a network controller. Each wireless device associates itself with a particular AP, with which it communicates. Each wireless device (which might be moving) determines from time to time if it has good communication with its associated AP, and whether it would have better communication with a different AP. Each AP might be coupled to a single device, a collection of devices, or to a computer network.
In any of these cases, the known art exhibits several problems.
A 1st problem is that multiple wireless devices might contend for communication through the AP. This might constrict the wireless devices and AP's from using their full communication ability. This might cause some wireless devices to obtain more or better communication service than others. This might reduce the ability of AP's to provide QoS (quality of service) guarantees that are needed for some uses of wireless devices, such as VoIP (voice over Internet Protocol) and other voice or video applications.
A 2nd problem is that handoff (deassociating a wireless device from a 1st AP, and associating that wireless device with a 2nd AP) can take substantial time in relation to the communication. Similar to the 1st problem, this might constrict the wireless devices and AP's from using their full communication ability. Similar to the 1st problem, this might reduce the ability of AP's to provide QoS guarantees that are needed for some uses of wireless devices, such as VoIP and other voice or video applications.
A 3rd problem is that access points currently support only 1 or 2 channels and access points on different channels in the same frequency band typically cannot be co-located. If 2 channels are supported, they are in different frequency bands, i.e. one on 2.4 GHz and one on 5 GHz, to prevent cross-channel interference. Therefore, any handoff must be spatial, i.e., from a 1st AP to a spatially separated 2nd AP. For example, since access points must be kept at some minimum distance from each other, handoff from channel 1 to channel 6 on the same AP and location cannot occur. Spatial handoff is much more difficult to optimize than handing off across channels in the same location to a multi-frequency access point.